Southern cave crayfish description

An aquatic crustacean that lives permanently in underground water systems, the southern cave crayfish (Orconectes australis) has a number of bizarre features that enable it to inhabit this highly unique subterranean habitat (2). The southern cave crayfish lacks functioning eyes and instead possesses enhanced tactile (touch) and olfaction (smell) senses, suited to a life in the dark (2). In addition, like many cave-dwelling species, the southern cave crayfish’s body is colourless and almost translucent (2).

Like all crayfish, this species has two pairs of antennae and five pairs of legs. The front pair is enlarged and bears large pincers (3). The female southern cave crayfish is slightly larger than the male (6).

The southern cave crayfish is one of the largest animals of its underground aquatic habitat (4), and its scientific name suitably reflects this, as ‘Orco’ is Latin for ‘god of the underworld’ and ‘nectes’ means ‘swimmer’ (5).

It is only recently that the southern cave crayfish has been elevated to the species level, based on genetic and geographic evidence (4). Prior to this, the southern cave crayfish was classed as one of two subspecies of Orconectes australis, O. australis australis, the other being O. a. packardi(7).

Related species

Southern cave crayfish biology

The southern cave crayfish is adapted to survive in the severe environmental conditions of cave ecosystems, which have stagnant, low-oxygen air and extremely limited food supplies. As a necessary consequence of limited food, the southern cave crayfish has evolved an extremely slow metabolic rate, much lower than that of other crayfish (2). The extremely slow metabolism results in a slow growth rate, low reproductive rate, and a long lifespan (6). At an estimated 19 to 50 years, the southern cave crayfish’s lifespan is extraordinarily long compared to other crayfish (6).

Female southern cave crayfish produce very few eggs, and hatching is very slow (2). In studies, few egg-bearing females have been observed in populations at any time (2). It is likely that mating does not occur every year and is a relatively rare event (2)(6). From the limited number of observations of egg-bearing females, egg-laying and hatching of the young appears to typically take place in autumn and early winter (6).

Southern cave crayfish range

The southern cave crayfish occurs in Alabama and Tennessee in the United States. Its range extends from Jackson and Madison Counties in Alabama, northward to the western edge of the Cumberland Plateau in Fentress County, Tennessee, and west into Morgan County, Tennessee (1).

Species with a similar range

Southern cave crayfish habitat

As an obligate cave-dwelling species, the southern cave crayfish is restricted to subterranean freshwater streams and pools, where it can be found in the water as well as up on the pool banks and cave walls (1).

Southern cave crayfish status

Southern cave crayfish threats

While the southern cave crayfish is not currently known to be facing any major threats (1), subterranean aquatic fauna are generally considered to be especially vulnerable, as they are restricted to a fragile habitat that is highly susceptible to degradation (4).

Southern cave crayfish conservation

Presently there are no species-specific conservation measures in place for the southern cave crayfish, as it is not considered to be threatened with extinction (1). However, it has been recommended that activities to protect the fragile habitat occupied by this species should be implemented. This could involve measures such as preventing pollution and gating cave entrances (4).

A lack of knowledge about this species means that further research would be beneficial in determining its abundance, as well as assessing whether it is being impacted by any major threats (1).

Glossary

Crustacean

An animal with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (parts of the mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.

Metabolic rate

The speed at which an animal uses energy.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

Day, L. (2007) Field Guide to the Natural World of New York City. The Johns Hopkins University Press, Baltimore, Maryland.

Huryn, A.D., Venarsky, M.P., and Kuhjada, B.J. (2008) Assessment of Population Size, Age Structure and Growth Rates for Cave Inhabiting Crayfish in Alabama: Final Report. State Wildlife Grant Project, Alabama.

Buhay, J.E. and Crandall, K.A. (2008) Taxonomic revision of cave crayfishes in the genus Orconectes, subgenus Orconectes (Decapoda: Cambaridae) along the Cumberland Plateau, including a description of a new species, Orconectes barri.Journal of Crustacean Biology, 28(1): 57-67.

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